ERVs are used to capture energy from the exhaust air stream and through the use of enthalpy-wheels it transfers a large portion of the waste heat back into outside air intake stream. By pre-treating the outside air, cooling and heating loads are reduced. ERVs are popular in regions with high outside air humidity or extremely low or high ambient outside air temperature. This is because energy transfer increases as the temperature difference between the occupied space and the outside air increases. ERVs operate during the occupied period of a building.
When ERVs first came to market, they were often not serviced correctly, in many cases causing the equipment to fail to deliver promised benefits. Today, fresh-air ventilation requirements on commercial buildings in on the rise. This has renewed interest in technologies that can minimize the financial impact of conditioning outside air. Accordingly, ERVs are once again becoming popular in the marketplace.